Generator Pitch

[PAFred]

Does anyone know of an easy way to determine (in the field)a generators pitch. In other words How can I figure out what the pitch of an existing generator so I know what to order to put on line with an older unit for paralleling?

 

[dpc]

One approach might be to measure the harmonic output of the generator. The percentage of harmonic voltages, particularly the 3rd should give a supplier a pretty good idea of the pitch.

 

[edison123]

Pitch is usually given in the generator manual. Else, contact the OEM or physically trace the pitch after opening the end covers.

Normally generator pitches are 5/6th.

 

[edison123]

Except in two pole machines, where it is more likely 2/3rd.

 

[rbulsara]

If the generator has the nameplate it should have a number for its "wiring arrangement". Take that number and consult the manufacturer or its rep. You can also use the sr.no.

The alternator also have the sr. no. or winding arrangement no. stamped (engraved) in its body.

 

[rbulsara]

i meant "on" the body..

 

[alehman]

If this is a packaged genset, it may take several phone calls. You need to find the alternator manufacturer. I've found the packager's records are not always accurate with such details.

 

[wolf39]

Assuming that we deal with a three-phase generator and a multiple turn coil winding:

First count the number of stator slots and divide this number by the number of poles. Then you've got the number of slots per pole (number of slot pitches per pole pitch). This number in most (but not all) cases is a fractional number.

Then determine the number of slot pitches between top layer of a coil and bottom layer of the same coil. This number always is a whole number, of course.

Divide the second number by the first number and you get the winding pitch. For large hydro generators winding pitches can vary between about 0.80 and 0.95. The higher this pitch number is the higher the voltage induced into this coil will be.

Wolf

http://WWW.HYDROPOWER-CONSULT.COM

 

[dpc]

Using your x-ray vision, of course.

 

[jimgineer]

Measuring the harmonic content would involve using what is called a spectrum analyzer. It performs a FFT across the frequency spectrum and would key you in on what the harmonic output of your 60Hz waveform was.

Then would come the hard part: If you're lucky, pull up a datasheet on a 5/6th pitch generator and it will let you know how much attenuation there is for the 3rd, 5th, 7th.. etc harmonic. Compare to the results you get on your spectrum analyzer.

I think that the better approach involved looking at the windings of the generator if you can, as Wolf mentioned. I don't know how difficult this might be based on actually being able to get to this area of the generator and make sense of it.

The BEST option, of course, is to get the nameplate information, and then find the manufacturer's datasheet information on what the pitch is.

 

[catserveng]

If you have a good motor and generator rewind shop in your area, check with them. Most of the rewind data includs pitch, and I've been able to get that kind of info from a rewinder when the manufacturer or his local rep was unable too.